Presently, there exist multi-core processor machines that have multiple cores servicing an operating system (OS) such as the Microsoft® Windows® 7 operating system for example. Such machines utilize an increased amount of power for each processor core that is running, which can be a disadvantage for those machines that operate under battery power, such as mobile devices. It would be beneficial, power-wise, to idle as many of the cores as possible, when certain power management conditions exist, perhaps temporarily during periods of stress.
However, an operating system (OS) such as the Microsoft® Windows® 7 does not support an increase/decrease in the number of active cores in its processor while operating. The reason the Microsoft® Windows® 7 OS does not support such “hot core” re-allocating is because the OS allocates resources and makes critical assumptions based on the cores present at boot time. The Microsoft® Windows® 7 OS does allow unused cores to be parked or disused, effectively shutting them off, but this is done only as a result of the OS' perception of loading, wherein a light loading condition, the OS can load balance and park cores.
One solution to the problem can be to use hypervisor software running between the OS and the processor hardware to present a virtual set of cores to the OS. In effect, the hypervisor software creates a false image of multiple cores to the OS, which leads the OS to believe it has multiple active cores, whereas the hardware actually may have less than all cores active. Unfortunately, hypervisor software is large, requiring a substantial amount of hypervisor code footprint and the need of virtualization support within processors to achieve a reasonable performance outcome. Moreover, there is a performance penalty introduced by the hypervisor software.
Another solution is “core parking” achieved using process affinity, wherein OS processes are physically assigned to one core, effectively parking any non-used cores. However, this is not a guaranteed technique since it is controlled by the OS, and is again a workload dependant function as perceived by the OS.
Accordingly, there is a need to rapidly reduce or increase the active cores that are servicing the operating system for power reasons, and to do so without regard to process loading in near real time. Further, it would be of benefit to dynamically allocate the active cores without rebooting the OS.
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The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.